1. Field of the Invention
This invention relates to a method for making a surface acoustic wave (SAW) device package, more particularly to a method for making a SAW device package using semiconductor processing techniques.
2. Description of the Related Art
A surface acoustic wave (SAW) device normally includes a piezoelectric substrate with a transducer-mounting surface, and transmitting and receiving transducers formed on the transducer-mounting surface for transmitting and receiving surface waves propagating along the transducer-mounting surface of the substrate. Each of the transmitting and receiving transducers is in the form of a thin metal film, and includes a pair of opposing bus bars with a plurality of fingers extending from the bus bars in an interdigital manner. The SAW device is required to be enclosed within an enclosure so as to form an air cavity to permit propagation of surface acoustic wave within the cavity. Due to the cavity required between the enclosure and the transducer-mounting surface of the substrate, the SAW device cannot be directly molded with a molding compound, which is commonly used for packaging semiconductor chips, such as memory chips, to form the enclosure thereon. As a consequence, conventional ways of forming the enclosure are normally conducted by forming a casing to enclose the SAW device.
FIG. 1 illustrates a conventional SAW device that is disclosed in U.S. Pat. No. 4,845,397 and that includes a SAW die 10, a cradle 20 constraining the SAW die 10, and a casing 2 enclosing sealingly the assembly of the SAW die 10 and the cradle 20.
The casing 2 includes a base 21, a cover 22 disposed over the base 21, and a spacer 23 interposed between and connected sealingly to the base 21 and the cover 22. The manufacturing process of the aforesaid conventional SAW device is complicated and is relatively expensive. Moreover, the size of the aforesaid conventional SAW device is relatively large, and is difficult to be reduced. As a consequence, combining the conventional SAW device with a printed circuit board and electronic components to form a SAW device package, which includes a molding compound encapsulating the SAW device, the electronic components, and a portion of the printed circuit board, is not possible.